Yes I have looked at other threads concerning fuel pump wiring, but cant find a solution for the problem I have.

Concerning the electrical wiring hook up diagram - I have the same instructions that are listed in other threads for aftermarket fuel pums and the wiring of them. When I started installing mine last night on my 99 deville, combination 3 is the one my deville has except for one thing. The problem is that both my black wires are the same wire gage!!! I dont have a small or a large black wire - Yes they are the same wire gage. How does one know which back wires goes where since they are the same size. I hooked it up last night and installed the tank, but it was pretty late and didnt get a chance to start it up. It was a 50/50 shot as to which wire goes where, and if it doesnt start I know where to start.

Re: Fuel pump wiring???

Sorry for the double posts. I did ohm out both blacks wires and both indicate grounds. neither had a greater resistance. Today, after searching for wiring printouts for the connector, I have found that one black wire (pin C) is ground for the pump, the other black (pin D) is ground for the sending unit. So the question is, will it matter if the grounds are crossed? I always thought ground is ground???

Re: Fuel pump wiring???

OK - So I get it all back together, and yes it started up and works great. So one of two things happened, either I got lucky and picked the right ground wires, or..... a ground, is a ground, is a ground!!!!

I would still like to know if it really matters which ground wire goes where or if it doesnt matter at all. If the fuel pump groung is connected to the fuel sender ground and vice versa, would it still work???

Re: Fuel pump wiring???

Sal, I'd like to know what pump was removed from the tank? Was it changed previous or is this the first pump replacement? Any markings on the pump shell you removed? What are the numbers? the Date code? Thx.

Re: Fuel pump wiring???

Originally Posted by ruaskier2

Sal, I'd like to know what pump was removed from the tank? Was it changed previous or is this the first pump replacement? Any markings on the pump shell you removed? What are the numbers? the Date code? Thx.

There are 3 or 4 different pumps/modules depending on car/model/year/engine. It would help if you updated your profile to show what car you're talking about ............

Re: Fuel pump wiring???

It was the original pump. Had 157,000 miles on it, and sorry, no info for the unit removed. The fuel sender stopped working and I grew tired of using the "gallons used" in the information center. I figured for the price of the sending unit, and the trouble to change it, might as well do the whole pump. Like I stated before, both black wires on the connector were the exact same gage.

Re: Fuel pump wiring???

Poke through the different pump modules in the RockAuto parts site. Click on the little pictures or the "INFO" tab to get to a blowup and/or more info on the part. For the fuel pump module, some of those tabs will also show the wiring harness supplied with the new module.

Some of the new modules even have a new, larger blade, flat, 4-pin connector that gets spliced into the existing pump module wiring. I have two spare pump modules, two different electrical connectors on the tops - one original square/round pin connector; one flat/flat-blade connector with new pigtail.

Re: Fuel pump wiring???

Rock auto is actually where I purchased it. model #FG0118, (gm p/n 25325871) The photo of the connector is exactly the one that was in my kit. The connector that I had to cut off on my fuel tank had the purple, grey, and 2 black wires. The problem was, acording to the instructions, is that the 2 black wires on the tank connector should have been 2 different gages. The pump wiring instructions said to hook the orange/black wire of the new connector to the smaller gage, black wire on the tank, and the other black wire on the new pump connector, to the larger black wire on the tank connector. Since both wires on the tank connector were the same gage, I couldnt determine which went where.

Research indicates the two black wires on the tank connector are ground for the pump (pin C), the other black is ground for the sending unit (pin D). Which leads me back to my original question, did I get get lucky hooking it up, or does it not matter since both are grounds? A ground is ground?????